Bitcoin Dominance: A measure of how much of the total crypto market cap that is comprised of Bitcoin.
i.e. 41% of Total Crypto Market Cap is BTC in this explanation.
When BTC Dominance increases, typically the value of alts decreases against BTC
Vice Versa.
When BTC Dominance decreases, typically the value of alts, increases against BTC.
There are of course other assumptions that must be made directionally to address these but this is a crash course on BTC.D